There are two specific aims of this program. The first is to detemine extent of craniofacial and dental abnormalities in the C57BL/6J - Hyp mouse, an animal model for human vitamin D-resistant rickets. The second is to determine the effectiveness of current therapeutic treatment upon the prevention and/or amelioration of these abnormalities. The long-term objectives of this program are to gain insight into some aspects of craniofacial growth (both normal and perturbed) and to obtain information that can be used tp prevent or ameliorate the craniofacial and dental problems that afflict humans with vitamin D-resistant rickets. We also hope to detemine whether genetic or hormonal factors are responsible for the increased severity of symptoms in affected males. We will use craniometry, roentgencepholography, biochemistry, histology and experimental surgery to obtain our results.